The present invention relates to an implantable device for administering a treatment solution. In addition, the present invention concerns an operating device for a syringe for filling the device.
For uniform administration of a treatment solution over a lengthy treatment period, e.g. in the field of chemotherapy, there are known infusion pumps which are implanted in the patient""s body.
U.S. Pat. No. 4,496,343 discloses an implantable infusion pump which has a medication reservoir that must be refilled at certain intervals. The disclosed infusion pump has a housing body which is divided by a membrane into two chambers. The first chamber contains the active treatment solution to be administered while the second chamber contains a propellant substance that is expandable under isobaric conditions. A housing port sealed by a puncturable septum is provided for transcutaneous refilling of the first chamber by an injection syringe.
To provide direct access to the catheter, the infusion pump has a third chamber connected by a channel to the first chamber for holding the active solution. The active solution flows through the channel from the first chamber into the third chamber and through a catheter out of the third chamber to the infusion site. The third chamber makes it possible to administer an additional quantity of active solution directly or to take samples. To administer the active solution or to take a sample using an injection syringe, a second housing port is provided and is sealed by a second puncturable septum.
Life-threatening situations can occur for a patient if the two septa are inadvertently confused. This is the situation when the quantity of active solution provided for the first chamber is injected partially or entirely into the third chamber for the bolus infusion or for sampling. In the case of morphine, for example, this can result in immediate apnea. It is relatively easy to confuse the two septa in practice because they are beneath the skin.
An object of the present invention is to increase the safety of implantable infusion pumps having an additional septum for a bolus infusion.
The present invention provides an implantable device for administering a treatment solution with a chamber (3) for holding the active solution to be administered, the chamber having a refilling port (6) which is sealed by a puncturable septum (5). A chamber (9) holds a treatment solution bolus, with the chamber having an inlet port (12) sealed by a puncturable septum (11). A connection (8) is provided for establishing a fluid connection between the chamber (3) for holding the active solution to be administered and an infusion site where the active solution is to be administered, as is a connection (13) for establishing a fluid connection between the chamber (9) for holding the active solution bolus and the infusion site. A conveyance mechanism (4) for conveying the active solution out of the chamber (3) for holding the active solution to be administered to the infusion site is also provided. The present invention is characterized in that the connection (13) for establishing a fluid connection between the chamber (9) for holding the active solution bolus and the infusion site include a device (14) which releases the flow path only when the active solution bolus is supplied to the chamber (9) at a pressure above a predetermined minimum pressure.
The present invention also provides an operating device for a syringe for filling the device with a holder (18) for attaching the barrel of the syringe, an operating element (21) for gripping the plunger of the syringe, and a drive device (22) for displacing the operating element so that the plunger is forced into the barrel of the syringe. The operating device is characterized in that the drive device (22) is designed so that the operating element (21) can be displaced out of a first position into a second position against a restoring force and can be locked in this position, and a releasing device (29) which releases the operating element is provided, the operating element being pushed back by the restoring force into the first position after being released.
The device according to the present invention for administering a treatment solution has a device which releases the flow path from the chamber for the bolus infusion to the site where the active solution is to be administered only when the active solution bolus is supplied to the chamber at a pressure above a predetermined minimum pressure.
Life-threatening situations due to sudden administration of a large quantity of active solution are prevented if the active solution for refilling the medication reservoir is always supplied only at a pressure below the minimum pressure. In case the septum of the medication reservoir is confused with the septum for the bolus infusion, the active solution cannot be administered because the fluid connection between the chamber for the bolus infusion and the infusion site will not be released.
The device clearing the flow path between the chamber for the bolus infusion and the infusion site only when a predetermined minimum pressure is exceeded not only prevents unintentional infusions but also prevents the active solution from reaching the chamber for the bolus infusion.
In a preferred embodiment, the device for clearing the flow path is a pressure control valve which is advantageously designed as a slitted disk, preferably made of silicone, with an opening pressure of 2 to 4 bar.
The device according to the present invention for administering a treatment solution is used together with an operating device which prevents the active solution from being supplied at a pressure above the predetermined minimum pressure when filling the medication reservoir. For refilling the medication reservoir, a traditional syringe is inserted into the operating device. The operating device has for this purpose a holder for attaching the barrel of the syringe, an operating device for gripping the plunger of the syringe and a drive device for displacing the operating element so that the plunger is forced into the barrel of the syringe.
For activation of the operating device, the operating element is prestressed against a defined restoring force, which causes the operating element to be pushed back to empty the syringe. The restoring force is such that the active solution is supplied from the syringe at a pressure which is below the minimum pressure of the device for clearing the flow path between the chamber for the bolus infusion and the infusion site. The pressure at which the active solution is supplied, however, is above the propellant pressure in the medication reservoir of the device for administering the active solution. A typical working range is between 1 and 1.5 bar.
The medication reservoir is filled when the tip of the syringe inserted into the operating device is beneath the septum of the chamber for holding the active solution when refilling the medication reservoir. However, if the tip of the needle is beneath the septum of the chamber for holding the active solution bolus, this effectively prevents an infusion administration error. Likewise, infusion is prevented if the tip of the needle is in one of the septa.
To administer a treatment solution bolus, a syringe for holding the active solution may be operated manually to build up a pressure above the predetermined minimum pressure.